Carburetor



Sept. 11, 1934.

s. F. BRIGGS CARBURE'I'OR Filed Sept. 21, 1932 2 Sheets-Sheet 1 Sept.11, 1934.

S. F. BRIGGS CARBURETQR 2 Sheets-Sheet 2 Filed Sept. 21, 1932 5/55/75/7flP/ S Patented Sept. 11, 1934 UNITED STATES PATENT OFFICE Briggs &Stratton Corporation, Milwaukee,

Wis a corporation of Delaware Application September 21, 1932, Serial No.634,126

14 Claims.

This invention relates to improvements in carburetors and has as anobject to provide a carburetor having novel means to facilitate startingof an internal combustion engine with which the carburetor is used.

Heretofore, various means have been employed to facilitate starting of acold engine. The conventional choke valve wasthe most commonly used, butthis method was open to many well known objections.

made in the past to obviate the necessity for a choke valve or toprovide automatic means for its control.

The present invention contemplates an improvement in carburetors wherebythe choke valve is entirely obviated and wherein during the initialstarting of the cold engine a substantial charge of fuel is quicklydrawn into the mixing chamber and thereafter until a predetermined totime at which the engine has attained a desired running temperature, asmaller quantity of auxiliary fuel is drawn into the carburetor mixingchamber.

With the above and other objects in view which will appear as thedescription proceeds, the invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

In the accompanying drawings, several com plete examples of the physicalembodiment of this invention is illustrated constructed according to thebest modes so far devised for the practical application of theprinciples thereof, andin which:

' Figure 1 is a fragmentary illustration of a .40 carburetor ofconventional design with portions.

thereof broken away and in section to illustrate the application of thisinvention thereto; and

Figures 2 and 3 illustrate slightly modified con,- structions.

Referring now more particularly to the accompanying drawings, thenumeral 5 represents the body of a conventional carburetor having aventuri 6 and a mixing chamber 7. The particular carburetor illustratedis of the down draft type with the mixing chamber and the throttle valve8 therein at the lower end, the main air inlet being at the upper end ofthe carburetor.

A fuel jet 9 is mounted within the mixing chambar with its outletorifice 10 positioned at the throat of the venturi and slightly above.the fuel Hence, efforts have been a supply line 13 and its level in thefloat chamber is maintained in the customary manner by the actuation ofa float 14.

Formed either as an integral part of the float chamber or as a separateunit, is a fuel reservoir 15. This fuel reservoiris communicated withthe float chamber through an inlet port 16 in the partition wall 17 andas the reservoir is vented in any suitable manner as by the provision ofa vent opening 18 in its upper wall, the fuel fills the reservoir 15 tothe level determined by the float. An outlet orifice 19 is formed in thebottom wall of the reservoir and a duct 20 connected there-.

with and debouching into the mixing chamber '7 directly adjacent thethrottle valve affords a communication from the reservoir to the mixingchamber. This communication is controlled by a valve 21 which in thepresent instance is in the form of a needle valve seating in the orifice19.

The valve 21 has a stem 22 extending upwardly through the reservoir tomount an armature 23 at its upper end. The armature 23 is arranged to beattracted to a'solenoid 24 upon energization thereof. The armature 23together with the weight of the valve 21 and its stem normally maintainsthe valve in its closed position, but when the solenoid 24 is energized,the attraction of the armature thereto opens the valve and establishescommunication from the reservoir to the mixing chamber.

The energization of the solenoid 24 is effected by the closing of acircuit diagrammatically illustrated and which comprisesa battery 25, amanually operable switch 26 and a thermostatically operable switch 2'7all connected in series withthe solenoid through conductors 28 and 29.The .manually operable switch 26 may be either the ignition switch ofthe internal combustion engine or some other switch operated inconjunction I therewith, and the thermally operable switch 27 consistsmerely of a bi-metallic strip 30 positioned adjacent a portion of theexhaust manifold 31.

The bi-metallic strip 30 is so arranged that at ambient temperatures itholds the switch 27 closed, but upon the manifold 31 becoming heated bythe normal operation of the engine, it flexes and opens the valve 2'7.

It is well known that in colder weather the difficulty of starting isincreased. Hence, it may be desirable to provide means for co-ordinatingthe functioning of the priming device with the 'metallic member 37 isengageable.

\that a maximum rate of flow ambient temperature. For this purpose, ithas been found efiective to regulate the rate of flow of fuel fromthereservoir 15 into the mixing chamber. and also to regulate the degree ofcommunication betwen the reservoir and the float chamber. Figures 2 and3 illustrate two practical embodiments of this feature. In Figure 2, theopening 16' which affords a communication between the float chamber 11and the reservoir 15, is controlled by a valve 33 carried at the outerfree end of the bi-metallic strip 34 rigidly secured to the wall 17, asat 35. The bi-metallic strip 34 is so arranged that a greater degree ofopening is effected during colder temperatures than under warmconditions.

Also, in the structure shown in Figure 2, the valve stem 22 is providedwith a series of stepped notches 36 with which the free end of a bentbi- The opposite end of the bi-metallic member 37 is fixed to the wall17, as at 38. This member is so formed that in cold weather a maximumopening is permitted but at warmer temperatures the degree of opening ofthe valve 21 is limited.

Coordination of the rate of flow of fuel from the float chamber into thereservoir with the ambient temperature may be also obtained by providinga second and larger orifice 39 in the wall 17 to communicate the floatchamber and reservoir, which orifice is controlled by a valve 40 mountedon a bi-metallic strip 41 similar to the strip 34. This valve 40 opensupon the temperature dropping below a predetermined point so is obtainedduring colder temperatures.

It is observed that in the embodiment'of the invention illustrated inFigure ,2, the duct 20 leading from the reservoir to the mixing chamberof the carburetor debouches into the carburetor outwardly of thethrottle valve, whereas in the disclosure of Figure 1, it is shown asentering the mixing chamber at a point above the throttle valve. Theexact location of this point. of communication may vary under differentconditions but at all times is maintained close to the edge of thethrottle valve in its normal substantially closed position.

' v Operation Assuming that the engine is at rest and cold, the thermalvalve 27 will be in its normal closed position, but the switch 26 willbe open. Consequently the solenoid 24 will be deenergized and the valve21 closed so that the reservoir 15 will be filled with fuel to the leveldetermined by the float 14.

When the engine is started the switch 26 will be closed. This closes thecircuit of the solenoid 24 to open the valve 21, whereupon the supplyoffuel contained within the reservoir will flow into the mixing chamber bygravity in the event the carburetor is of the down draft typeillustrated, or if it is the conventional up draft type the suctionwithin the mixingv chamber adjacent the throttle valve will draw thefuel up into the mixing chamber.

A rich mixture will thus be conducted to the engine and as the outletorifice 19'is substantially twice the size of the inlet 16, the fuelwithin the reservoir will be discharged into the mixing chamber fasterthan it will flow from the fioat chamber into the reservoir. As a resultall of the accumulated fuel within the reservoir will be discharged intothe mixing chamber during the initial starting period and thereafterauxil-= iary fuel willcontinue to flow into the mixing chamber throughthe duct 20, but the volume thereof will be restricted to the amountdetermined by the area of the inlet orifice 16.

This condition will obtain until the engine has reached its normaloperating temperature at which the bi-metallic strip 30 of the thermalswitch 27 will be actuated by the heat radiated from the manifold 31.When this occurs the cir- Figure 2 is obviously substantially the sameas has been described, with the exception that the rate of flow of thefuel from the reservoir to the carburetor mixing chamber is controlledthermostatically.

From the foregoing description taken in connection with the accompanyingdrawings, it will be readily apparent to those skilled in the art towhich an invention of the character described appertains, that thisinvention affords a simple and eflicient means for discharging auxiliaryfuel into the mixing chamber of a carburetor to obtain the desired richmixture, without the necessity for the conventional choke valve.

- What I claim as my invention is:

1. In a carburetor having 'a mixing chamber, a fuel reservoir, means tosupply fuel to the reservoir at a predetermined rate of flow, means todischarge fuel from the reservoir to the mixing chamber at a rate offlow greater than that of the supply to the reservoir, and avalve tocontrol the discharge from the reservoir to the mixing chamber, wherebythe reservoir fills with' fuel when the valve is closed and empties whenthe valve is open at a rate determined by the area of the discharge andthereafter supplies fuel to the mixing chamber at a rate determined bythe inlet.

2. In a. carburetor having a mixing chamber with a throttle valvetherein, means to supply fuel directly to the mixing chamber adjacentthe throttle valve comprising, a fuel reservoir having an inlet and anoutlet, the inlet being connected with a source of fuel supply and beingof smaller area than the outlet whereby fuel discharges from thereservoir at a faster rate than it flows into the reservoir, means toconnect the discharge of the reservoir with the mixing chamber, and avalve to control the discharge, the reservoir filling with fuel when thevalve is closed and emptying upon opening of the valve to supply fuel tothe mixing chamber at a rate of flow determined by the area of theoutlet until the reservoir is emptied and thereafter supplying fuel tothe mixing chamber at a rate of fiow determined by the area of theinlet.

3. In a carburetor having a mixing chamber with a throttle valveoperating therein, means to supply fuel to the mixing chamber at a pointadjacent the throttle valve comprising, a reservoir having an inlet forcommunicating the reservoir with a fuel supply and an outlet of greaterarea than the inlet whereby fuel can discharge from the reservoir at arate faster than it can to open the valve, the contents of the reservoirdischarging into the mixing chamber upon opening of the valve at a rateof flow determined by the area" ofthe outlet and thereafter the fuelentering the reservoir through its inlet discharging into the mixingchamber, whereby the volume of fuel discharged into the mixing chamberis reduced after the contents of the reservoir are emptied, and saidthermostatically controlled means operating after a predetermined timeto close the valve.

4. In a carburetor having a mixing chamber provided with a throttlevalve, a fuel reservoir having an inlet through which fuel enters thereservoir and an outlet of greater area than the inlet so that thecontents of the reservoir may be drained at a rate greater than saidcontents can be replenished, a duct connecting the outlet with themixing chamber adjacent the throttle valve, a valve for closing theoutlet of the reservoir, electromagnetic means to control the positionof the valve, an electric circuit adapted when closed to energize theelectromagnetic means and open the valve to enable the contents of thereservoir to be discharged into the mixing chamber and thereafter toenable fuel to pass into the mixing chamber from the supply through thereservoir and the duct at a rate of fiow determined by the area of theinlet, and thermal means operable to open the circuit and effect closingof the valve.

5. In a carburetor having a float chamber and a mixing chamber providedwith a throttle valve, means to supply fuel directly to the mixingchamber adjacent the throttle valve comprising, a reservoir communicatedwith the float chamber through an inlet opening, said reservoir havingan outlet opening of greater area than the inlet opening whereby thecontents of the reservoir may be discharged at a rate faster than it canbe replenished through the inlet opening, a duct leading from the outletopening to the mixing chamber adjacent the throttle valve, a valve toclose the outlet opening, electromagnetic means to open the valve andpermit the contents of the reservoir to be discharged into the mixingchamber to supply fuel to the mixing chamber at a rate determined by thearea of the discharge and then to supply fuel to the mixing chamber at alesser rate determined by the area of the inlet opening, and thermallyresponsive means to control the electromagnetic means, said thermallyresponsive means operating within a predetermined period after theopening of the valve to close the valve.

6. In combination with the carburetor and a part of an internalcombustion engine susceptible to becoming heated during normal operationthereof, the carburetor having a mixing chamber provided with a throttlevalve, means to supply fuel directly to the mixing chamber adjacent thethrottle valve during starting of the internal combustion engine,comprising a fuel reservoir having an inlet through which fuel enters ata predetermined rate of fiow and an outlet through which fuel dischargesat a greater rate of flow, a duct connecting the outlet with the mixingchamber, a valve for the outlet, electromagnetic means to control thevalve, an electric circuit adapted to be closed upon starting of theinternal combustion engine to energize the electromagnetic means andopen the valvewhereby the contents of the reservoir discharges into themixing chamber at the rate of flow determined bythe area of thedischarge opening and thereafter fuel is discharged into the mixingchamber at the rate of flow determined by the inlet, and thermal meansoperable upon the attainment of a predetermined temperature at said partof the internal combustion engine susceptible to be heated to open thecircuit and deenergize the electromagnetic means to enable the valve toclose.

7. In a carburetor having a mixing chamber, means to supply auxiliaryfuel to the mixing chamber comprising, a fuel passage debouching intothe mixing chamber, said fuel passage having a restricted inlet throughwhich fuel enters and a metering orifice spaced from the restrictedinlet and larger than said inlet, the space in the fuel passage betweenthe inlet and metering orifice affording a reservoir, and a valve toclose the metering orifice, whereby a supply of fuel is retained in thereservoir between the inlet and metering orifice when the valve isclosed and whereby fuel is conducted to the mixing chamber by saidpassage when the valve is opened first in a large volume and thereafterin a smaller volume.

, 8. In a carburetor having a mixing chamber, an auxiliary fuel passagedebouching into the mixing chamber, said fuel passage having arestricted inlet through which fuel enters and a metering orifice spacedfrom the restricted inlet and larger than said inlet, the space betweenthe restricted inlet and the metering orifice being enlarged to afford afuel reservoir, a valve to close the metering orifice and cause'thereservoir to fill with fuel, and automatic means to open the valve andrelease the supply of fuel from the reservoir for passage to the mixingchamber whereby auxiliary fuel passes to the mixing chamber at a rate offlow determined by the area of the metering orifice until the reservoiris emptied and thereafter at a rate of flow determined by the area ofthe restricted inlet.

9. In a carburetor having a mixing chamber and a throttle valve therein,a fuel reservoir, a thermostatically controlled communication leadingfrom the reservoir to the mixing chamber adjacent the throttle valve toconduct fuel from the reservoir to said mixing chamber, andthermostatically responsive means to control the rate of flow of fuelfrom the reservoir to the mixing chamber.

10. In a carburetor having a mixing chamber and a throttle valvetherein, a fuel reservoir, a communication between the reservoir and themixing chamber, means to supply fuel to the reservoir to pass from thereservoir through said communication to said mixing chamber,thermostatically responsive means to control, the fuel supply to thereservoir, a valve to close said communication, and thermostaticallyresponsive means to control the position of said valve.

11. In a carburetor having a mixing chamber and a throttle valvetherein, a fuel reservoir, a communication between the reservoir and themixing chamber, means to supply fuel to the reservoir to pass from thereservoir through said communication to said mixing chamber,thermostatically responsive means to control the fuel supply to thereservoir, a valve to close said comber, the reservoir filling with fuelwhen the valve is closed and emptying when the valve is open at a ratedetermined by the area of the discharge and thereafter supplying fuel tothe mixing chamber at a rate determined by the supply of fuel to thereservoir.

13-. In a carburetor having a mixing chamber, a fuel reservoir, means tosupply fuel to the reservoir, thermostatic means to control the rate offuel supply to the reservoir, means to discharge fuel from the reservoirto the mixing chamber, a valve to control the discharge of fuel from thereservoir to the mixing chamber, whereby the reservoir fills'with fuelwhen the valve is closed and empties when the valve is open, the rate offlow of the fuel from the reservoir to the mixing chamber beingdetermined by the area of the discharge until the reservoir is empty andthereafter by the rate of flow into the reservoir, and thermostaticmeans to control the valve.

14:. In a carburetor having a mixing chamber, a fuel reservoir, means tosupply fuel to the reservoir, thermostatic means to control the rate offuel supply to the reservoir, means to discharge fuel from the reservoirto the mixing chamber, a valve to control the discharge of fuel from thereservoir to the mixing chamber, whereby the reservoir fills with fuelwhen the valve is closed and. empties when the valve is open, the rateof flow of the fuel from the reservoir to the mixing chamber beingdetermined by the area of the discharge until the reservoir is empty andthereafter by the rate of flow into the reservoir, means to open saidvalve, and thermostatic means to control the degree of opening of thevalve.

STEPI-EN F. BRIGGS.

